The invention relates to a continuous casting mould for an I-shaped preliminary section.
The continuous casing of preliminary sections for producing profile steel, in particular I-shaped girders, has been known since 1968. Worldwide, only a few steelworks have hitherto produced such preliminary girder sections on a large scale since their production requires considerable know-how. The general trend towards casting sections to nearly final dimensions has increased interest in casting preliminary sections. In spite of this trend, the difficulties associated with the casting of such cross-sections have not yet been satisfactorily overcome. The main problem today is still the sticking of the billet in the mould, in particular when casting parameters do not correspond to the predetermined tape of the mould. Furthermore the expenditure involved in producing molds is very high.
German Auslegeschriift 1 282 861 discloses an ingot mould for the continuous casting of I-shaped sections. In accordance with the shrinkage of an I-shaped section the mould cavity has positive taper on the flange outer sides and negative taper on the flange inner sides. In order to improve machining of the mould cavity, the mould is constructed in two parts along a plane parallel to the web of the I-shaped section.
In order to cool the billet skin to a sufficient degree and to prevent the billet from sticking in the mould, the positive and negative mould tapers have to be adapted to the steel grade, the casting temperature, the casting speed, etc. If the billit sticks in the mould when a breakdown occurs, it can be removed from the two-part mould by opening the latter. However, such ingot moulds are expensive to manufacture. In addition, with moulds of this type different casting speeds easily lead to breakdowns and increased wear.
U.S. Pat. No. 4,805,685 further discloses a mould for casting I-shaped sections. In the case of this mould recesses in the mould cavity cross-section for the web part are shaped according to predetermined ratios. Transitional areas between the web part and the flange parts are defined precisely by a flat angle of inclination. These gentle transitions simplify the production of the mould cavity by dipensing with undercuts and negative mould cavity taper. However the teachings of this patent are remote from the casting of parts to nearly final dimensions and necessitate corresponding extensive rollowing and shaping.